It is especially popular on the island of Java, where it is a staple source of protein. Like tofu, tempe is made from soybeans, but it is a whole soybean product with different nutritional characteristics and textural qualities. Tempe’s fermentation process and its retention of the whole bean give it a higher content of protein, dietary fiber, and vitamins. It has a firm texture and an earthy flavor, which becomes more pronounced as it ages.[3][4]

History

Tempe being sold on Java, early 20th century

Tempe originated in Indonesia, almost certainly in Java, more precisely central or east Java,[1] with an estimated discovery between a few centuries ago to a thousand years or more.[7]:145 Around the 12th to 13th century, a type of food was mentioned as kadêlê in an old Javanese manuscript, Serat Sri Tanjung.[6] However, it is not clear whether kadêlê refer to processed fermented soy or not, since the term in Javanese today refer to “soybeans”. The earliest known reference to it as têmpê appeared in 1815 in the Serat Centhini.[6]

The invention of tempe is connected to tofu production in Java. The tofu-making industry was introduced to Java by Chinese immigrants circa the 17th century. Chinese Indonesian historian Ong Hok Ham suggests that tempe was accidentally produced as the by-product of the tofu industry in Java; as discarded soybeans caught the spores of a whitish fungus that was found to be edible.[6] Three detailed, fully documented histories of tempe, worldwide, have been written, all by Shurtleff and Aoyagi (1985, 1989, and 2001).

Production

Making tempe by wrapping boiled soybeans in banana leaves

Tempe begins with whole soybeans, which are softened by soaking, and dehulled, then partly cooked. Specialty tempe may be made from other types of beans, wheat, or may include a mixture of beans and whole grains.

The principal step in making tempe is the fermentation of soybeans which undergo inoculation with Rhizopus spp. molds, a type of filamentous fungus most widely used for the production of tempe.[8] For example, a fermentation starter containing the spores of fungusRhizopus oligosporus or Rhizopus oryzae is mixed in.[9] The beans are spread into a thin layer and are allowed to ferment for 24 to 36 hours at a temperature around 30°C (86°F). The soybeans have to cool down to allow spore germination and abundant growth of mycelium. Later, the temperature of the beans will naturally rise and rapid mold growth happens for around 4 hours. As mold growth declines, the soybeans should be bound into a solid mass by the mycelium. In good tempe, the beans are knitted together by a mat of white mycelium. Typically, tempe is harvested after 48 hours of fermentation with its distinguishable whitish color, firm texture, and nutty flavor. Extended fermentation time results in an increase in pH and undesirable color darkening in the tempe.[10]

During the fermentation process, optimal time of fermentation, temperature, oxygen, humidity, and pH levels are required to encourage the growth of the Rhizopus mold, while discouraging the growth of undesired microorganisms.[11] The pH level should be kept around 3-5 by adding a mild acidulant such as vinegar, lactic acid, or acetic acid, thereby favoring mold growth and restricting the growth of spoilage microorganisms.[12] Oxygen is required for Rhizopus spp. growth, but should be maintained at low levels to prevent the production of undesired microorganisms. Under conditions of lower temperature, or higher ventilation, gray or black patches of spores may form on the surface—this is not harmful, and should not affect the flavor or quality of the tempe.[13] This sporulation is normal on fully mature tempe. A mild ammonia smell may accompany good tempe as it ferments, but it should not be overpowering.

Traditional tempe is often produced in Indonesia using Hibiscus tiliaceus leaves. The undersides of the leaves are covered in downy hairs (known technically as trichomes) to which the mold Rhizopus oligosporus can be found adhering in the wild. Soybeans are pressed into the leaf, and stored. Fermentation occurs resulting in tempe.[14] In particular, the tempe undergoes salt-free aerobic fermentation.[15]

Determining quality

Once tempe is produced, it is divided into three categories based on its quality: good, unfinished, and inedible. Good tempe includes beans that are bound into a firm, compact cake by a dense, uniform, white mycelium, which should permeate the entire cake. Furthermore, the beans should be barely visible. The odor of good tempe should be pleasant, clean, subtly sweet or resemble the aroma of mushrooms. The entire tempe should lift as a single, cohesive cake without crumbling when shaken gently. Unfinished tempe has beans that are bound together loosely by a sparse white mycelium, hence it crumbles easily. Unfinished tempe should be incubated longer unless it has been incubated more than 8 hours past the recommended time. If it has been incubated for enough time and still remains unfinished, it should be discarded. Inedible tempe has beans with foul odor, resembling strong ammonia or alcohol, indicating the development of undesirable bacteria due to excess moisture or overheating. Inedible tempe cake is wet, slimy, and mushy with a collapsed structure. Its color is tan to brown and mold develops in sparse patches.[12]

Packaging

Food grade wrapping paper and perforated polyethylene bags are the most suitable materials for packaging tempe. They have demonstrated good retention of the quality of tempe and extension of the shelf life of tempe for three days compared to fresh tempe. Appropriate packaging is important as it provides optimum oxygen supply and temperature for inoculation and fermentation to occur during processing.[16] Tempe is a perishable food and must be wrapped and placed into the refrigerator or freezer immediately after incubation or other processing steps such as blanching. In the refrigerator or freezer, stacking of tempe should be minimized to prevent overheating and the undesirable, gradual continuation of fermentation, both of which shorten the storage life of tempe. Even under cold temperature, tempe continues to respire and undergo slow decomposition from microorganisms and its natural enzymes. Therefore, tempe should be well cooled for at least two to five hours in a cooler before they undergo further packaging.[12] Tempe packaged in perforated polyethylene bags is usually repacked inside another labeled, non-perforated bag for distribution and sale, and for easier labeling. If the tempe is only packaged in one perforated bag, the label must be directly attached to the perforated surface with the use of government food contact approved adhesive.[16] They are then bulk packed in cartons and returned to the refrigerator or freezer to await shipment.[12]

The soy carbohydrates in tempe become more digestible as a result of the fermentation process. In particular, the oligosaccharides associated with gas and indigestion are greatly reduced by the Rhizopus culture. In traditional tempe-making shops, the starter culture often contains beneficial bacteria that produce vitamins such as B12[17][18] (though it is uncertain whether this B12 is always present and bioavailable).[19] In western countries, it is more common to use a pure culture containing only Rhizopus oligosporus, which makes very little B12 and could be missing Citrobacter freundii and Klebsiella pneumoniae, which have been shown to produce significant levels of B12 analogs in tempe when present.[20] Whether these analogs are true, bioavailable B12 has not been thoroughly studied yet.[21]
The fermentation process also reduces the phytic acid in soy,[22] which in turn allows the body to absorb the minerals that soy provides.

Preparation

Tempe burger

In the kitchen, tempe is often prepared by cutting it into pieces, soaking in brine or saltysauce, and then frying. Cooked tempe can be eaten alone, or used in chili, stir fries, soups, salads, sandwiches, and stews. Tempe’s complex flavor has been described as nutty, meaty, and mushroom-like. It freezes well, and is now commonly available in many western supermarkets, as well as in ethnic markets and health food stores. Tempe can be steamed, marinated, thinly sliced, blackened, or crumbled into sauces and stews.[23]

Tempe performs well in a cheese grater, after which it may be used in the place of ground beef (as in tacos). When thin-sliced and deep-fried in oil, tempe obtains a crisp golden crust while maintaining a soft interior. Its sponge-like consistency makes it suitable for marinating. Dried tempe (whether cooked or raw) is more portable and less perishable and may be used as a stew base. Sometimes when tempe is diced and left, they will create white feathery fluff which bonds the cut—this is the Rhizopus mold still growing—this is normal and perfectly edible.

Types

Sliced tempe kedelai (soy tempe)

The most common tempe is made from fermented soybeans. However, traditionally other ingredients such as ampas tahu (tofu dregs/okara), ampas kelapa (coconut dregs) and peanuts may be used in a fashion similar to the tempe making process, although perhaps using different fungi or attracting other microbes.

Tempe kedelai

Also called tempe kedele or tempe dele, or simply just tempe. The most common and widely known tempe, made from controlled fermentation of soybeans.

Tempe gembus

Tempe gembus

Soft and fluffy tempe made from soy pulp or tofu dregs.[24][25] Tempe gembus usually can be found in traditional markets of Java, at a price lower than that of common soybean tempe. It is made into a variety of dishes; for example it can be battered and/or fried, used in sayur lodeh, or tempe bacem. Tempe gembus is known by different names across Java; for example as tahu cokol or tahu susur in Temanggung.[24]

Tempe oncom

Tempe oncom, or simply onchom, is made from peanutpress cake or soy dregs. Among fermented bean products, oncom is more prevalent in West Java, where it serves as the main ingredient in various Sundanese cuisine traditional dishes, including oncom goreng, oncom leunca, and nasi tutug oncom. There are two types of oncom: a bright red-orange kind with Neurospora sitophila, and a black one with the same fungi as tempe uses.[26]

Tempe menjes kacang

Menjes kacang

A specialty of Malang, the rough textured tempe menjes kacang is made from black soybeans mixed with other ingredients, such as peanut dregs, cassava fiber, and soybean meal. The process of making menjes kacang is quite similar to black oncom.[27]

Tempe bongkrèk

Tempe bongkrèk is a variety of tempe from Central Java, notably Banyumas regency, that is prepared with coconut dregs. This type of tempe has led to several cases of fatal food poisoning,[28] as it occasionally gets contaminated with the bacterium Burkholderia gladioli, and the unwanted organism produces toxins (bongkrek acid and toxoflavin) from the coconut, besides killing off the Rhizopus fungus due to the antibiotic activity of bongkrek acid.[25]

Fatalities from contaminated tempe bongkrèk were once common in the area where it was produced.[29] Thus, its sale is now prohibited by law; clandestine manufacture continues, however, due to the popular flavor. The problem of contamination is not encountered with bean and grain tempe, which have a different composition of fatty acids that is not favorable for the growth of B. gladioli, but encourages growth of Rhizopus instead. When bean or grain tempe has the proper color, texture and smell, it is a very strong indication the product is safe. Yellow tempe bongkrèk is always highly toxic due to toxoflavin, but tempe bongkrèk with a normal coloration may still contain lethal amounts of bongkrek acid.[30]

Oat tempe

A new form of tempe based on barley and oats instead of soy was developed by scientists at the Swedish Department of Food Science in 2008. It can be produced in climatic regions where it is not possible to grow soybeans.[31]

Process

Sometimes tempe is left to ferment further, creating a pungently stronger “almost rotten” tempe called tempe semangit in Javanese.

The wrappings used in tempe making can contribute to its flavor and aroma. Though some prefer the traditional banana, waru or teak leaf, readily available plastic sheet wrappings have been increasingly widely used.

Common tempe

Common soybean tempe that has undergone sufficient fermentation process.

Tempe semangit

In Indonesia, ripe tempe (two or more days old) is considered a delicacy. Names include tempe semangit (stinky tempe) in Java, hampir busuk (the almost rotten) tempe or tempe kemarin (yesterday tempe). Having a slightly pungent aroma, small amounts are used as a flavoring agent in traditional Javanese sayur lodeh vegetable stew.

Tempe murni

Pure soybean cake, tempe made in plastic wrap without any fillings or additives such as grated raw papaya. This was meant to create a more “hygienic and pure” tempe free from any impurities or unwanted microbes.

Cooking methods and recipes

Sautéed tempe with string green beans, an Indonesian dish

The simplest way to cook tempe is by frying. It is both deep-fried and stir-fried. However, there are several cooking methods and recipe variations. Among others are:

Tempe goreng

Probably the simplest and most popular way to prepare tempe in Indonesia. The tempe is sliced and seasoned in a mixture of ground garlic, coriander seeds and salt, and then deep fried in palm oil.[34] The tempe might be coated in batter prior to frying, or directly fried without any batter.

Tempe bacem

Tempe bacem is a traditional Javanese dish originating in Central Java. Bacem is a Javanese cooking method of braising in spices and palm sugar. The tempe is first braised in a mixture of coconut water, palm sugar, and spices including coriander seeds, shallots, galangal, and bay leaves, and then briefly deep-fried. The result is a moist, sweet and spicy, dark-colored tempe. Tofu may also be used, yielding tahu bacem.[35]

Tempe mendoan

Frying tempe mendoan

Cooked tempe mendoan

This variation is often found in Purwokerto. The word mendoan originates in the Banyumas regional dialect, and means “flash-fried”. The tempe is first dipped in spiced flour before quickly frying in very hot oil, resulting in a product that is cooked on the outside, but raw or only partially so on the inside. It has a limp, soft texture compared to the more common, crisp, fully fried tempe.

Tempe kering

Also known as kering tempe (lit: “dry tempe”), or sambal goreng tempe if mixed with plenty of hot and spicy sambalchili pepper sauce. It is a crispy, sweet and spicy, fried tempe.[36] The raw tempe is cut into small sticks and thoroughly deep-fried until no longer moist, and then mixed with palm sugar, chili pepper or other spices, or with sweet soy sauce. Often it is mixed with separately fried peanuts and anchovies (ikan teri). This dry tempe will keep for up to a month if cooked and stored properly.

Tempe orek or orak-arik tempe

This variation is almost identical to tempe kering, but is more soft and moist.[37] The sweet taste is due to generous addition of kecap manis (sweet soy sauce).[38]

Tumis tempe or oseng tempe

Stir-fried tempe with vegetables such as green bean, basil, or onion, with spices.[39] Other recipes might add coconut milk for a milky-colored, and rather moist, stir-fried tempe.

Tempe penyet

Fried tempe mixed with sambal chili paste in a mortar and pestle. Usually served in addition to other penyet dishes, such as ayam penyet (chicken) or iga penyet (ribs).

Tempe satay

Sate kere (Javanese for “poorman’s satay”) from Solo in Central Java is made from fluffy tempe gembus.[40] Ground tempe can also be made into a thick sauce, such as in sate ambal, a chicken satay from Kebumen, Central Java where tempe flavored with chili and spices replaces the more common peanut sauce.[41]

Kripik tempe

Kripik tempe snack crackers; a thinly sliced tempe, battered and deep fried until crispy. It is popular across Java, but notably produced in Bandung, West Java.

Preservation

Freshly made, raw tempe remains edible for a few days at room temperature. It is neither acidic nor does it contain significant amounts of alcohol. It, however, does possess stronger resistance to lipid peroxidation than unfermented soybeans due to its antioxidant contents.[44]

Cooked as tempe kering, the deep fried and seasoned bits of tempe can last for a month or more and still be good to consume, if cooked correctly and stored properly in air-tight jar. The deep frying process removes the moisture, preventing further fermentation and deterioration, thus prolonging its shelf life.

Non-refrigerated fresh tempe

Tempe can be sold and consumed fresh within 48 hours once removed from its incubator. It is commonly transported to the market in its incubation container (e.g. polyethylene bag, banana leaf wrapper, etc.) and placed in the shade. In areas with warmer climates, tempe can be kept at room temperature for 1–3 days before it becomes overripe. In locations with more temperate temperatures, it can keep for 1–4 days but will usually need to be refrigerated to prevent spoilage.[12]

Refrigeration

Fresh refrigerated tempe should be sealed in a labeled polyethylene bag and kept in temperatures below 4˚C (40˚F). It can be kept at this temperature for 3–5 days and sometimes, even as long as a week. Storage life could be extended to 2 or 3 weeks if the tempe is blanched or steamed prior to refrigeration due to the inactivation of enzymes and destruction of bacteria.[12]

Freezing

Freezing is the preferred way to preserve tempe due to its capability for wide distribution. Tempe can be frozen whole or in slices, depending on preference. During the freezing process, whole tempe is placed in its perforated wrapper whereas sliced tempe is packaged in a labelled polyethylene bag prior to being sealed in an outer bag and then frozen immediately. This method will keep for months with only a small loss of texture and flavor.[12]

Blanching

Blanching tempe by steaming or parboiling helps to extend the storage life by preventing bacterial growth, stopping mold growth and inactivating enzymes. Steaming appears to have a less negative effect than parboiling in terms of texture, flavor and nutritional value. Blanching is a great method for preserving tempe prior to refrigeration, though not as beneficial for tempe that is to be frozen.[12]

Dehydration

Air tray drying

Tempe can be dried via the air tray drying method. Cubes of tempe placed on steel, mesh bottom trays are dried by the circulating hot air dryer. After the product is finished, they can be cut into 1inch squares at 200˚F for 90 to 120 minutes in order to reduce moisture content to 2-4%. When placed in moisture proof Pliofilm bags, the tempe has a shelf life of several months at room temperature. Although this is a convenient method that produces a shelf stable product without requirement of refrigeration, the process of hot air drying can cause a significant loss of nutritional content such as the soluble solids and nitrogen protein content.[12]

Sun drying

This preservation method is most economical out of all methods. The tempe can be blanched prior to dehydration to preserve flavor and prolong shelf life. Tempe is exposed to internal solar dryer temperature of 180-200˚F in this method. A disadvantage of this method is that sunlight can destroy some of the vitamin B12 of tempe.[12]

Freeze drying

This method is the most expensive out of all dehydration methods but provides the advantage of long stable shelf life at room temperature and an excellent retention of soluble nutrients (nitrogen protein and other solids). The product undergoes quick freeze at 50 ˚F and then dried at a moderate temperature inside a strong vacuum. Due to the pricey nature of the equipment, the final product price will be higher than tempe preserved through other methods.[12]

Spray drying

As this method is traditionally used for small particles, it is used to produce tempe powder for products such as soups, breads, tortillas, etc. However, this method can be expensive due to the bulky nature of the equipment.[12]

Deep frying

This method produces ready to eat tempe products. Different types of oils such as rapeseed, soy, safflower, peanut, or coconut oil is heated to 350˚F in the deep fryer. The tempe is deep fried until golden brown and crisp, and then cooled quickly in a sterile environment to be sealed in Pliofilm bags and stored in a cool, dry place. The shelf life of this product lasts around a week but can be extended if the tempe is sun dried or oven dried prior to deep frying.[12]